The human hand is an amazing machine that can pick up, move and place objects easily, but for a robot, this “gripping” mechanism is a vexing challenge. Opting for simple elegance, researchers from Cornell University, the University of Chicago, and iRobot have bypassed traditional designs based around the human hand and fingers, and created a versatile gripper using everyday ground coffee and a latex party balloon.

They call it a universal gripper, as it conforms to the object it’s grabbing rather than being designed for particular objects, said Hod Lipson, Cornell associate professor of mechanical engineering and computer science. The research is a collaboration between the groups of Prof. Lipson, Heinrich Jaeger at the University of Chicago, and Chris Jones at iRobot Corp. It was published recently online in “Proceedings of the National Academy of Sciences”.

“This is one of the closest things we’ve ever done that could be on the market tomorrow,” Prof. Lipson said. He noted that the universality of the gripper makes future applications seemingly limitless, from the military using it to dismantle explosive devises or to move potentially dangerous objects, robotic arms in factories, on the feet of a robot that could walk on walls, or on prosthetic limbs.

Here’s how it works: An everyday party balloon filled with ground coffee – any variety will do – is attached to a robotic arm. The coffee-filled balloon presses down and deforms around the desired object, and then a vacuum sucks the air out of the balloon, solidifying its grip. When the vacuum is released, the balloon becomes soft again, and the gripper lets go.

Prof. Jaeger said coffee is an example of a particulate material, which is characterized by large aggregates of individually solid particles. Particulate materials have a so-called jamming transition, which turns their behavior from fluid-like to solid-like when the particles can no longer slide past each other.

This phenomenon is familiar to coffee drinkers familiar with vacuum-packed coffee, which is hard as a brick until the package is unsealed.

“The ground coffee grains are like lots of small gears,” Prof. Lipson said. “When they are not pressed together they can roll over each other and flow. When they are pressed together just a little bit, the teeth interlock, and they become solid.”

The project was supported by the Defense Advanced Research Projects Agency.